The laser light source module is mounted in a scanning display device. This scanning display device operates so that laser light, which is formed by combining several laser beams emitted from a laser element, is two-dimensionally scanned on a screen with a mirror element to display an image. This type of display device is demanded to increase the brightness of the image to be displayed. Hence, it is necessary to increase a laser output. However, if an attempt is made to increase the laser output, the temperature of each laser element significantly rises.
If the laser element temperature rises, the oscillation wavelength of each laser element changes to reduce image quality and shorten the life thereof. This degrades the performance of the laser light source module. Hence, it is important that an appropriate structure be employed to increase the heat dissipation of the laser element.
In general, the laser element is combined with a thermoelectric cooling element and a small-size fan to present an excessive temperature rise in the laser element. On the other hand, a laser light source module mounted in a small-size scanning display device, is demanded to reduce its power consumption because it is battery-driven.
As such being the case, the electrical power used for cooling needs to be reduced. Thus, a structure for thermally connecting the laser element to a heat diffusing base is being studied as it reduces the temperature rise in the laser element without using electrical power for cooling.
For example, Japanese Unexamined Patent Application Publication No. 2009-204692 discloses that a thermally conductive member is connected between a metal housing and an LED, which is a light source for a display device, to increase the area of heat dissipation.
Meanwhile, Japanese Unexamined Patent Application Publication No. 2003-273438 discloses that leads of an optical module are disposed on a lateral surface of the optical module to bring a bottom surface of the optical module in contact with a heat diffusing base as a heat sink. This structure ensures that the heat of the optical module is easily transferred to the heat diffusing base.
The above-mentioned related arts can prevent an excessive temperature rise in the laser element by thermally connecting the heat sink to an LED or each laser element that acts as a heat source. However, in a laser light source module comprising several laser elements as a light source for a display device, several laser beams need to be accurately combined to each other.
The reason is that an image cannot be accurately displayed if the light beam emitted from any laser element deviates from an appropriate direction. Therefore, it is necessary to employ a structure that inhibits a deviation of an optical axis. According to the above-mentioned related arts, the thermally conductive member is disposed in a direction perpendicular to the optical axis. Consequently, when the above-mentioned related arts are employed, the optical axis is deviated from the appropriate direction because of deformation caused by a temperature rise in the thermally conductive member.
The present invention has been made in view of the above circumstances and provides a highly reliable laser light source module that is structured to not only prevent an excessive temperature rise in a laser element but also inhibit a deviation of an optical axis of laser light caused by a temperature rise.